Testing and fracture mechanics analysis of strength effects on the fatigue behavior of HFMI-treated welds

摘要

In this paper, recent fatigue tests conducted on welded specimens subjected to high frequency mechanical impact (HFMI) treatment are described, geometry measurements and metallurgical analyses of the tested specimens are presented, and efforts to estimate the test results using a nonlinear fracture mechanics model are discussed. The specimens were fabricated from 9.5-mm-thick (3/8 in.) aluminum (5083-H321) and high-strength steel (ASTM A514) plate. The specimen geometry and preparation followed procedures used in previous studies on mild steel (CSA 350W). Fatigue tests were performed on the as-welded and impact-treated specimens under two loading histories (constant amplitude with and without periodic under-loads) at several equivalent stress ranges. Residual stress distributions were determined by x-ray diffraction. In addition, weld toe geometry measurements were obtained using silicon impressions and micro-hardness distributions were obtained on polished weld samples for each material type. This information was used to establish parameter values for a nonlinear fracture mechanics analysis. The employed fracture mechanics model is reviewed in this paper, and its benefits as a tool for modelling the fatigue behavior of impact-treated welds are discussed. Following this, the effectiveness of the model in estimating the test results for the three materials is assessed.